This invention relates to a liquid level sensor and, more particularly, to a liquid level sensor that uses fiber optics to measure the center displacement of a corrugated diaphragm fiber.
The detection of liquid level is one of many functions for which fiber-optic sensors are more suitable than their electrical counterparts, especially in noisy or hostile environments. Much commercial attention has been focused on a simple on-off liquid-level switch which senses the sudden increase in optical radiation loss from an uncladded, bent optical fiber making contact with a liquid. An array of such "point" sensors may be used to detect a number of discrete levels; however, such a system cannot provide a continuous indication of liquid level.
Various other sensors are known in the art for measuring liquid level, either discretely or continuously. While often ingenious, the commercial potential of these sensors may be limited if: (1) they require fibers or other optical components to be immersed in the liquid, which immersion could modify the optical characteristics of the fiber as a result of "wetting" or corrosion; (2) they require light to pass through a liquid whose refractive or absorptive properties effect the operation of the sensor (thereby limiting their operation with certain liquids, especially opaque ones); or (3) they are complex and rely on components which are not common in the fiber-optics industry. Simplicity, availability of components, and low cost are highly attractive features of any commercially viable sensor.